In the design of switching power supplies, such as AC-to-DC switching power supplies in the 5 kW to 10 kW range usable in driving the motors of commercial air conditioners, there has always been a general desire to reduce the cost of the power supply. Despite this, power supply designs continue to have certain characteristics and standard design aspects. Cost often remains undesirably high, despite the desire to reduce it, because how to reduce the power supply manufacturing cost has been, and continues to be, an unknown and nonobvious thing. There are many different parts and aspects of a power supply to be focused on and to which effort can be devoted in the quest to reduce cost. Changing the design of one part of the circuit may actually serve to increase the cost of another part of the circuit. Reducing cost in certain respects may not be possible due to associated reductions in performance of the power supply. How to reduce overall power supply cost while still meeting performance or reliability and other requirements on the power supply is difficult.
It is known that the size of the magnetic component or components of many power supply circuits can often be reduced if the magnetics of the power supply can be made to switch at a higher frequency. But just increasing the frequency at which the power supply is switched would not reduce power loss in the short transient switching periods. There is a time when a switching transistor of a power supply is being turned on. It is initially substantially non-conductive, and then after the transient time it is considered to be on and substantially conductive. But during the intervening transient time, it has an appreciable non-zero resistance which due to current flow through the transistor at that time translates into power losses. Similarly, there is a time when a switching transistor of a power supply is being turned off. It is initially on and is substantially conductive, and then after the transient time it becomes nonconductive and is considered to be off. But during the intervening transient time, it has an appreciable non-zero resistance which translates into power losses. If the actual switching of the transistor could be made faster, then power loss during these transient times could be reduced. The associated reductions in power losses might serve to reduce the cost of heat sinks and/or fans and other parts of the power supply that would be otherwise necessary for removing unwanted heat from the power supply. Despite it being known in the art that there are such undesirable power losses during transient switching conditions, knowledge of how to reduce or eliminate these losses in a commercially-realistic way has remained elusive and unknown.